Coupling ring for ventilation ducts



FIG. 1 is a front perspective view of an oval coupling ring of the new design.

FIG. 2 is a rear perspective view of the coupling ring of the new design with a rear three-lip element.

FIG. 3 is a rear view of the coupling ring.

FIG. 4 is a side view of the coupling ring.

FIG. 5 is a front view of the coupling ring.

FIG. 6 is an end view of the coupling ring; and,

FIG. 7 is a cross-section of the coupling ring at a central straight portion of the same, showing said rear element, section line VII—VII in FIG. 5. 

The ornamental design for a coupling ring for ventilation ducts, as shown. 